[S-TT40] Synthetic Aperture Radar and its application

[STT40-01] InSAR and GNSS measurement of urban vertical land motion in New Zealand and Japan.

*Jesse Ryan Kearse¹, Tim Stern², Ian Hamling³, Sigrun Hreinsdottir³, Simon Lamb² (1.Kyoto University, 2.Victoria University of Wellington, 3.GNS Science)

Densely populated urban coastal strips are most at risk from the effects of relative sea-level rise. At the same time, anthropogenic activities associated with urbanization, such as groundwater withdrawal and rechange, land reclamation and cut and fill operations can lead to vertical land motion (VLM), further exacerbating the risk to urban infrastructure. For New Zealand we generate high-resolution urban maps (10 m) of VLM using Sentinel-1 InSAR data between 2018-2021, and calibrated using GNSS observations. This analysis reveals large swaths of the urban coastlines are subsiding faster than -0.5 mm/yr and 10% of the coastlines are subsiding faster than -3.0 mm/yr. This analysis documents highly-localised hotspots of LLS, with subsidence rates exceeding -10.0 mm/yr in some cases. For Osaka VLM data is generated from 5 years of Sentinel-1 data between 2017-2022, and calibrated using dense GNSS observations. Vertical land motion anomalies (both uplift and subsidence) are identified, and correlate spatially with the location of known active faults beneath Osaka city. The processes driving vertical deformation in Osaka could include fault creep, and long-term (multi-annual) changes in ground water within aquifers across the fault zones. This is the subject of ongoing research.